Digital Cable Question

Thanks for all of your kind replies gents, they were very informative.

At least one site offers two lengths: 12 inches, or 5 meters!! Which apparently are the best lengths for less reflections being a problem.

The usual recommendation, if the cable is not very short (less than 12 inches) is 1.5 meters, or about 5 feet. See this paper.

Length beyond 1.5 meters would not provide additional benefit in terms of reflection timing (unless perhaps the output signal of the source component has unusually slow risetimes and falltimes). The additional length could, however, conceivably result in increased noise pickup from ground-loop or rfi/emi effects, thereby worsening jitter. Also, if hi rez formats are involved a 5 meter length could actually cause reflection timing to become more of a problem rather than less.

These length recommendations, btw, are generally intended to further improve the situation where a reasonably good impedance match exists to begin with. A severe mismatch will not necessarily be helped by using a 12 inch or less cable length.

The 1.5 meter length probably would help a severe mismatch in the case of redbook data rates, but not necessarily for hi rez rates. In the case of hi rez data rates, if the impedance mismatch is severe enough, reflections corresponding to a given signal edge (i.e., a given 0 to 1 or 1 to 0 transition) may keep propagating back and forth across the length of the cable enough times to cause distortion on the following signal edge.

Regards,
-- Al

I'm using a Clarity Cable XLR as a digital cable and it smokes my JPS Superconductor Q and Morrow DIG4 AES/EBU. Soundstage is more defined and precise.

Craig,
In theory they shound be different but the reality maybe some thing else. Some brands, ASI Liveline and Kondo-Japan for example use the same analog cable for digital with great results. I happened to use the Liveline and it`s just a remarkable digital cable. Srajan Ebaen(6 Moons Editor) found this cable better than his long time reference, the Stealth Varidig Sextet(one man`s opinion). As with all things audio, listen and judge yourself,

The main difference is that an unbalanced digital cable is (presumably and hopefully) designed to have a "characteristic impedance" of 75 ohms, within a tight tolerance, while chances are that an analog interconnect will not be.

A digital audio signal has frequency components that extend well into the radio frequency region. At those frequencies, it is necessary that the characteristic impedance of the cable, the output impedance of the component driving the cable, and the input impedance of the destination component, all be the same (within a narrow tolerance). Otherwise VSWR effects, aka "transmission line effects," will result in reflections back and forth along the cable which will degrade waveform quality, causing increased jitter or even misclocking and data corruption.

That said, I would expect that some analog interconnects will work satisfactorily in some systems.

Regards,
-- Al